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MWSI Project Phase II Conjunctive Use Summary Report - DRAFT Generic Welljield Cost Analysis August 22, 1995 To evaluate costs related to ground water production from the northern and southern metro areas, spreadsheets were prepared to calculate the well and pump installation, pipeline, treatment, operation, and maintenance costs related to the production of 2,000 af/yr from the northern and southern well field locations, Costs were calculated over an assumed 20-year project term with a discount rate of five percent. The energy cost is $0,05 per kilowatt hour and the annual inflation rate was 1,5 percent. Explanations of the parameters and cost calculations contained in the cost spreadsheets are included in Appendix A, In the northern wellfield the 2,000 af/yr appropriation was divided between the Denver, Upper Arapahoe, Lower Arapahoe and Laramie-Fox Hills aquifers based on the relative production capacity of each aquifer, i,e., more water was taken from the better aquifers. In a similar manner the 2,000 af/yr volume was divided between the Denver, Arapahoe and Laramie- Fox Hills aquifers for the southern well field, Additional inputs to the analysis include: static water level, specific capacity, well diameter, well drilling cost-per-foot, and system pressure, The static water level and specific capacity are used to determine the pumping water level in the well. Additionally, a decline in the static water level was included for ea~h year, The pumping water level and system pressure are used in the total dynamic head calculation. A system pressure of 50 psi was used in the analysis, Nominal pump/motor horsepower numbers, based on estimated production ranges and total dynamic head ranges, were used to estimate minimum acceptable casing/screen sizes, These were normalized to 8" and 10" diameter nominal sizes for the cost analysis. The analysis assumes constant pumping throughout the 20-year period, The following table summarizes the volume of water and number of wells by aquifer for the northern and southern well fields. Table 2 Northern and Southern 2,000 AflYr Wellfields Aquifer Northern Wellfield Volume (af/yr) Southern Wellfield Number of Wells Volume (af/yr) Denver 401 5 670 Upper Arapahoe 320 5 nla Lower Arapahoe 592 5 nla Arapahoe nla nla 970 Laramie-Fox Hills 687 3 360 Total 2,000 18 2,000 Number of ~ 2 nla nla 2 1 5 There are four cost-calculation spreadsheets for the northern well field presented as Tables 3 to 6 and three cost-calculation spreadsheets for the southern wellfield, Tables 7 to 9, 5